6814437: G1: remove the _new_refs array

The per-worker _new_refs array is used to hold references that point into the collection set. It is populated during RSet updating and subsequently processed. In the event of an evacuation failure it processed again to recreate the RSets of regions in the collection set. Remove the per-worker _new_refs array by processing the references directly. Use a DirtyCardQueue to hold the cards containing the references so that the RSets of regions in the collection set can be recreated when handling an evacuation failure.

Reviewed-by: iveresov, jmasa, tonyp

hotspot/src/share/vm/gc_implementation/g1/heapRegion.cpp

@@ -683,6 +683,8 @@ oops_on_card_seq_iterate_careful(MemRegion mr,
     return NULL;
   }
 
+  assert(!is_young(), "check value of filter_young");
+
   // We used to use "block_start_careful" here.  But we're actually happy
   // to update the BOT while we do this...
   HeapWord* cur = block_start(mr.start());